Effects of Pseudomonas putida and Rhizophagus irregularis alone and in combination on growth, chlorophyll, carotenoid content and disease complex of carrot

Effects of Pseudomonas putida and Rhizophagus irregularis alone and in combination were observed on Meloidogyne incognita , Alternaria dauci and Rhizoctonia solani disease complex of carrot ( Daucus carota ). Rhizoctonia solani caused a higher reduction in plant growth, chlorophyll and carotenoid content followed by A. dauci and M. incognita . Use of P. putida and R. irregularis alone and in combination caused a significant increase in plant growth, chlorophyll, carotenoid and reduced disease indices, galling and nematode multiplication. Application of P. putida caused a higher increase in plant growth, chlorophyll and carotenoid and reduced disease indices, galling and nematode multiplication greater than R. irregularis. Application of P. putida plus R. irregularis was best for the management of M. incognita , A. dauci and R. solani disease complex. Root colonization of R. irregularis / P. putida was high when alone but colonisation by both was increased when inoculated together. M. incognita , A. dauci and R. solani reduced root colonization caused by P. putida and R. irregularis. Disease indices were rated on 1–5 scale. Leaf blight and crown rot indices were nearly 3 when A. dauci and R. solani were inoculated respectively. Disease indices were nearly 5 when pathogens under study were inoculated in combination of 2 or 3. Application of P. putida or R. irregularis with A. dauci or R. solani reduced indices to nearly 2 while both biocontrol agents together reduced indices to nearly 1. In other treatments, disease indices were 2–4 out of 5. The principal components analysis showed significant correlations among various studied attributes with 82.10% overall data variability.